As the demand for fuel increases worldwide, there is increasing interest in producing fuels and blending components from sources other than crude oil. Often referred to as a renewable source, these sources include, but are not limited to, plant oils such as corn, rapeseed, canola, soybean, microbial oils such as algal oils, animal fats such as inedible tallow, fish oils and various waste streams such as yellow and brown greases and sewage sludge. A common feature of these sources is that they are composed of glycerides and Free Fatty Acids (FFA). Both triglycerides and the FFAs contain aliphatic carbon chains having from about 8 to about 24 carbon atoms. The aliphatic carbon chains in triglycerides or FFAs can be fully saturated, or mono, di or poly-unsaturated.
U.S. Pat. No. 4,300,009 discloses the use of crystalline aluminosilicate zeolites to convert plant oils, such as corn oil, to hydrocarbons for use as gasoline and chemicals such as para-xylene. U.S. Pat. No. 4,992,605 discloses the production of hydrocarbon products in the diesel boiling range by hydroprocessing vegetable oils such as canola or sunflower oil. Finally, US 2004/0230085 A1 discloses a process for treating a hydrocarbon component of biological origin by hydrodeoxygenation followed by isomerization.
Applicant has developed a process which comprises one or more steps to hydrogenate and deoxygenate (via catalytic decarboxylation, decarbonylation and/or hydrodeoxygenation) and isomerize the feedstock. The effluent from the isomerization zone is separated into at least a vapor portion and a liquid portion comprising hydrocarbons that can used as a fuel, such as a diesel range or aviation range fuel.
Impurities in such feedstock fats and oils, such as feedstocks derived from plant, animal or microbe (bacteria, algae, fungi), result in increased capital spend, higher operating expenditure, and reduced net yields of products. Such feedstock often require pretreatment (such as with mineral acids or with ion exchange resins) to remove contaminants such as phosphorus, nitrogen and metals. While the pretreatment may remove the contaminants, up to 5% of feedstock may be lost in the pretreatment processing steps. Since the feedstock cost can represent a significant portion of the production cost, even a small loss of feedstocks can impact on operating cost. Additionally, as a result of the contaminants, a guard bed is typically required to protect the more expensive downstream catalysts for the deoxygenation and isomerization steps. The guard bed may increase capital cost and operating cost, and may also potentially reduce the number of operating days in a year due to guard bed maintenance and adsorbent change. Furthermore, the current processes typically utilize hydrogen which is high purity (99.9% hydrogen) and has a high pressure (greater than 2 MPa). Hydrogen or hydrogen production feedstock such as natural gas availability in certain areas may be low, making the cost and use of hydrogen an important factor for many refiners. Finally, some feedstocks contain polyunsaturated lipids (such as those derived from fish oil, salicornia or certain algae) which have a reduced shelf life due to oxidation stability issues.
Therefore, it would be desirable to provide processes for the production of hydrocarbons from a renewable feedstock which can lower the amount of high purity and high pressure hydrogen required.
Additionally, it would be desirable to provide processes for the production of hydrocarbons from a renewable feedstock which increase the shelf life of the feedstocks allowing for more efficient batch production.